The disclosure relates to a pressure-regulating arrangement with a pressure-regulating valve according to the description below and to a closed hydraulic circuit with a pressure-regulating arrangement of this type.
In the case of pressure-regulating valves, an outlet pressure of an outlet connection is intended to be adjusted and, for example, kept constant even under a variable inlet pressure of an inlet connection. For this purpose, a valve body of the pressure-regulating valve requires a control surface which is acted upon by the outlet pressure and at which the outlet pressure acts upon the valve body counter to a spring in the direction of reducing a flow opening from the inlet connection to the outlet connection. In this case, the flow opening can be regarded as an adjustable restrictor. Of course, regulation is undertaken only if the inlet pressure is greater than the adjusted outlet pressure.
Furthermore, pressure-regulating valves are known, in which, in addition to the connection to the inlet pressure, the outlet connection can also be relieved to a tank connection. The outlet pressure can therefore be actively reduced even if said outlet pressure rises above the regulating pressure for whatever reason. For this purpose, the valve body is centered in a central regulating position and can be moved in a first direction in order to reduce the outlet pressure and in an opposite direction in order to increase said outlet pressure. The two different valves may also be linguistically delimited from each other by only the valve with the possibility of connecting the regulating outlet to the tank being referred to as a pressure-regulating valve, and the valve without this possibility being referred to as a pressure-reducing valve.
It is known from the applicant's product information RA 92003-A/03.09 or RA 92003-A/06.09 to use pressure-regulating valves of this type for regulating an adjusting pressure which is used to adjust a main pump, the suction volume of which is adjustable, of a closed circuit. For this purpose, an above-described pressure-regulating valve is connected on the inlet side to a feed line into which feed pressure medium is conveyed by a feed pump coupled to the main pump. An orifice plate is arranged in the feed line, through which the feed pressure medium passes, at which a variable pressure drop arises depending on the rate of feed pressure medium passing therethrough. The valve body of the pressure-regulating valve—in addition to the above-described action thereupon by the adjusting pressure to be regulated and by the spring or the springs—is acted upon in the opening direction by the pressure upstream of the orifice plate and in the closing direction by the reduced feed pressure downstream of the orifice plate. Therefore, a rotational-speed-dependent outlet pressure at the pressure-regulating valve and therefore a rotational-speed-dependent adjusting pressure for an adjustable main pump are produced and regulated via pressure-regulating arrangements of this type, since the feed pump is conventionally a fixed displacement pump, and therefore the rate of the feed pressure medium which said pump conveys depends on the rotational speed of said pump and therefore on the rotational speed of the main pump.
A disadvantage of regulating an outlet pressure via pressure-regulating arrangements of this type is that, due to the orifice plate, there is a fixed dependency of the outlet pressure on the rotational speed of the variable displacement pump.
In the event of use of the rotational-speed-dependent control of a variable displacement pump, a certain dependency of the adjusting pressure on the rotational speed is not the most suitable for all of the operating ranges and in particular not for all uses of the variable displacement pump. For different uses, orifice plates having different flow cross sections are therefore also used.
By contrast, the disclosure is based on the object of providing a pressure-regulating arrangement with a pressure-regulating valve, in which the dependency of the outlet pressure on the volumetric flow of a main line supplied on the inlet side and the characteristic of the outlet pressure can be changed and also readjusted depending on the volumetric flow. This object is achieved by a pressure-regulating arrangement with the features described below.
With regard to a hydraulically closed circuit with a pressure-regulating valve which serves for the rotational-speed-dependent control of a variable displacement pump, it is the object to be able to adapt the components of the closed circuit to the requirements of different use situations in a simple manner. This object is achieved by a circuit with the features described below.